It almost looks to me that the wires are connected to the bottom side of a bayonet style fuse clip, and with the heat radiating from the top of the wire on C phase, my best guess would be a loose spring clip on a fuseholder.

I have to agree , C phase connection appears loose. Heat is at higher temps. at lug connection, then as it follows the wire lead it begins to cool. This could be a sub panel, motor starter, light control,power termal connections in a control center/box,etc.